Keyboard support assembly

ABSTRACT

An articulated support assembly for a computer keyboard. The assembly includes a platform for supporting a computer keyboard. A parallelogram linkage pivotally interconnects the platform assembly to an attachment member secured to a support surface. A releasable retaining means prevents movement of the platform toward a lowered position relative to the support surface. Pivotal movement of the platform alters the distance between pivot axes of the parallelogram linkage to disengage the retaining means and allow movement of the platform toward either a lowered or a raised position relative to the support surface.

BACKGROUND

The present invention relates to articulated support assembly adapted for adjustably supporting a computer keyboard along one edge of a horizontal support member, and particularly to such support assembles that are attached to a bottom surface of the support member.

The art is replete with articulated support assemblies adapted for adjustably supporting a computer keyboard along one edge of a horizontal support member. The various prior art assemblies typically include locking mechanisms to maintain the support assemblies at a desired height. The locking mechanisms include “levered” locking mechanisms in which a lever or handle must be operated to release and re-secure the support assembly, and “leverless” locking mechanisms in which, typically, the keyboard platform itself is manipulated to release and re-secure the support assembly. Existing support assemblies and their associated locking mechanisms often fail to provide the desired combination of stability, adjustability and ease of use desired by the user.

SUMMARY

One aspect of the invention described herein provides an articulated support assembly adapted for adjustably supporting a computer keyboard from a horizontal support surface. In one embodiment according to the invention, the support assembly comprises: an attachment member adapted to be attached to the horizontal support surface; a platform assembly having an upper surface adapted to have a computer keyboard supported thereon, the upper surface having a predetermined orientation with respect to the horizontal support surface; a vertically swingable parallelogram linkage having elongated first and second links each having a first end and a second end, the first ends of the elongated first and second links pivotally interconnected to the platform assembly, and the second ends of the elongated first and second links pivotally interconnected to the attachment member, such that the first and second ends of the first and second links each have a pivot axis, and such that the linkage allows vertical displacement of the platform assembly relative to the support surface while maintaining the predetermined orientation of the upper surface; a releasable retaining means coupling the first link to the attachment member, the releasable retaining means moveable between an engaged position for preventing vertical movement of the platform assembly toward a lowered position relative to the horizontal support surface, and a disengaged position for allowing vertical movement of the platform assembly toward either a lowered or a raised position relative to the horizontal support surface; and means for altering the distance between the pivot axes of the second link, wherein altering the distance between the pivot axes of the second link moves the releasable retaining means between the engaged position and the disengaged position.

In another embodiment according to the invention, the support assembly comprises: an attachment member adapted to be attached to the horizontal support surface; a platform assembly having an upper surface adapted to have a computer keyboard supported thereon; a first support arm adapted for mounting the platform assembly on the attachment member, a first end of the first support arm pivotally mounted to the platform assembly for pivotal movement of the platform assembly about a first platform pivot axis, a second end of the first support arm pivotally mounted to the attachment member for pivotal movement about a first attachment member pivot axis; a second support arm adapted for mounting the platform assembly on the attachment member, a first end of the second support arm pivotally mounted to the platform assembly for pivotal movement of the platform assembly about a second platform pivot axis, a second end of the second support arm pivotally mounted to the attachment member for pivotal movement about a second attachment member pivot axis; wherein the first platform pivot axis, second platform pivot axis, first attachment member pivot axis and second attachment member pivot axis are parallel to each other, and wherein the first and second platform pivot axes, the first and second attachment member pivot axes, and the first and second support arms are positioned to define a parallelogram linkage; and first releasable retaining means between the first support arm and the attachment member, the first releasable retaining means moveable between an engaged position for preventing rotating movement of the first support arm toward a lowered position relative to the attachment member, and a disengaged position for affording rotating movement of the first support arm toward either a lowered or a raised position relative to the attachment member; wherein the first releasable retaining means is moved from the engaged position to the disengaged position by pivotal movement of the platform assembly about the first platform pivot axis.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described with reference to the accompanying drawings wherein like reference numerals refer to like parts in the several views, and wherein:

FIG. 1 is a perspective illustration of a first embodiment of an articulated support assembly according to the present invention;

FIG. 2A is a side elevational illustration of the articulated support assembly of FIG. 1, shown supporting a keyboard and attached to a horizontal support member and illustrating a range of positions in which the support assembly can be placed;

FIG. 2B is a side elevational illustration of the articulated support assembly of FIG. 1, shown supporting a keyboard and attached to a horizontal support member and illustrating a storage position in which the support assembly can be placed;

FIG. 3 is a perspective illustration of a top side of the articulated support assembly of FIG. 1 with a keyboard platform and mounting track removed, and with a cover removed from a support arm to show the releasable retaining means;

FIG. 4 is a perspective illustration of a bottom side of the articulated support assembly of FIG. 1 with a keyboard platform and mounting track removed;

FIG. 5 is an enlarged fragmentary sectional illustration taken approximately along line 5-5 of FIG. 3 and illustrating a pawl assembly in an engaged position;

FIG. 6 is an enlarged fragmentary sectional illustration taken approximately along line 5-5 of FIG. 3 and illustrating a pawl assembly in a disengaged position;

FIGS. 7A and 7B are exploded and assembled illustrations, respectively, of the tilt support arm of the articulated support assembly of FIG. 1;

FIG. 8 is a perspective illustration of a top side of the articulated support assembly of FIG. 1 with components removed to show the path and connections of the cable actuator for the releasable retaining means;

FIGS. 9A and 9B are side elevational illustrations of the articulated support assembly of FIG. 1, illustrating pivotal movement of the platform assembly to move the releasable retaining means to a disengaged position.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” “leading,” “trailing,” etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments of the present invention can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

Referring now to FIGS. 1-9B, there is shown a articulated support assembly 10 according to the present invention that is adapted for adjustably supporting a computer keyboard 11 along one edge 13 of a horizontal support member 12 (e.g., a desk or table top) that has a bottom mounting surface 14 (see FIGS. 2A and 2B).

Generally, the articulated support assembly 10 comprises an attachment member 16 adapted to be attached to the bottom mounting surface 14 of the horizontal support member 12 in spaced relationship adjacent its edge 13. Also included is a platform assembly 18 having a generally planar upper surface 20 adapted to have computer keyboard 11 supported thereon. A vertically swingable parallelogram linkage 30 attaches the platform assembly 18 to the attachment member 16, and allows vertical displacement of the platform assembly 18 relative to the bottom mounting surface 14 of the horizontal support member 12 while maintaining a predetermined orientation of the platform assembly upper surface 20 with respect to the horizontal support member 12.

In one embodiment attachment member 16 is coupled to a swivel assembly 32, which is in turn coupled to a track slide bracket 34. Swivel assembly 32 affords pivotal movement about the axis of bolt 36 (seen in FIG. 3), while track slide bracket 34 affords linear movement of support assembly 10 along a length of the bracket 34.

The parallelogram linkage 30 of support assembly 10 is best illustrated in FIGS. 2A and 2B. As is understood by those skilled in the art, a parallelogram linkage includes two pairs of parallel sides, pivotally connected at the four corners (i.e., pivot axes) of the parallelogram linkage. As the angles between adjacent sides of the parallelogram change, opposing sides of the parallelogram always remain parallel to one another. In the present invention, linkage 30 includes four parallel pivot axes defining the corners of the linkage 30: first and second platform pivot axes 40 and 42, respectively, and first and second attachment member pivot axes 44 and 46, respectively. First and second platform pivot axes 40, 42 are fixed in position with respect to platform assembly 18. First and second attachment member pivot axes 44, 46 are fixed in position with respect to attachment member 16. An upper link or support arm 48 extends between first platform pivot axis 40 and first attachment member pivot axis 44, while a lower link or support arm 50 extends between second platform pivot axis 42 and second attachment member pivot axis 46.

As best seen in FIG. 2A, as platform assembly 18 is moved between a lowered position and a raised position, the upper surface 20 of the platform assembly 18 maintains a constant predetermined orientation (i.e., tilt angle) with respect to the bottom mounting surface 14 of support member 12. In FIGS. 2A and 2B, the upper surface 20 of platform assembly 18 is shown substantially parallel to the support surface 12.

In the illustrated embodiment, the linkage 30 uses two upper support arms 48 a, 48 b (collectively upper support arms 48) positioned on opposite sides of lower support arm 50 (seen in FIGS. 1, 3 and 4). The upper support arms 48 a, 48 b commonly pivot about first platform pivot axis 40 and first attachment member pivot axis 44, and effectively act as a single upper support arm 48 in the linkage 30. However, the spacing of upper support arms 48 a, 48 b across the width of platform assembly 18 provides improved stability against torsional movement of platform assembly 18 when being used.

Typically, horizontal support member 12 is a desk or similar work surface, and the bottom mounting surface 14 has a height in the range of approximately 28 to 30 inches above a floor. In one embodiment, upper support arms 48 and lower support arm 50 have lengths sufficient to position upper surface 20 of platform assembly 18 approximately 10 inches or more above mounting surface 14, such that the articulated support assembly 10 may be used by an individual in a standing position.

In one embodiment, the platform assembly 18 includes an upper platform 52 providing planar upper surface 20, and a lower platform mounting plate 54 configured for mounting the platform 52 to the parallelogram linkage 30. In this manner, different platforms 52 (having different sizes, shapes, mouse pads, etc.) may be used with the support assembly 10 and commonly mounted using the platform mounting plate 54. In other embodiments, the upper platform 52 and platform mounting plate 54 may be formed as a single component, or as a combination of more than two components.

By means of an upper support arm mounting bracket 60, platform mounting plate 54 is mounted to a generally U-shaped rigid support member 62. Support member 62 includes an elongate central portion 64 and generally parallel end portions 66 projecting in the same direction from the opposite ends of the central portion 64. The elongate central portion 64 is aligned with first platform pivot axis 40. Upper support arm mounting bracket 60 secures platform mounting plate 54 on the central portion 64 of support member 62 for pivotal movement of the platform assembly 18 about the first platform pivot axis 40, with the upper surface 20 of the platform assembly 18 parallel to the first platform pivot axis 40.

First ends 70 of upper support arms 48 a, 48 b are adapted for mounting to the end portions 66 of the support member 62, while second ends 72 of upper support arms 48 a, 48 b are adapted for connection to attachment member 16 for pivotal movement about first attachment member pivot axis 44. Releasable retaining means or ratchet means 80 are provided between the upper support arms 48 a, 48 b and the attachment member 16. The releasable retaining means or ratchet means 80 are moveable between an engaged position (FIG. 5) that prevents revolving movement of the upper support arms 48 a, 48 b (and thus platform assembly 18) toward a lowered position relative to the attachment member 16, and a disengaged position (FIG. 6) that affords revolving movement of the upper support arms 48 a, 48 b (and thus platform assembly 18) toward either a lowered or a raised position relative to the attachment member 16.

In one embodiment, the upper support arms 48 a, 48 b each comprise two pairs 74 of mating polymeric moldings. First end 70 of each pair 74 of mating polymeric moldings encloses an end of the central portion 64 and one of the end portions 66 of the support member 62. The end portions 66 are attached to support arms 48 a, 48 b by bolts 82. Second end 72 of each pair 74 of mating polymeric moldings contains ratchet means 80. Engagement of the second ends 72 with the attachment member 16 is maintained by a bolt and washer assembly 82 that extends through openings in the attachment member 16 and in the second end 72.

The releasable retaining means or ratchet means 80 is best seen in FIGS. 5 and 6. Ratchet means 80 are described with respect to only one of the upper support arms 48 a, 48 b, but it is understood that ratchet means 80 are associated with each of the upper support arms 48 a, 48 b. The ratchet means 80 comprises a pivot gear 90 fixed to the attachment member 16 by bolt and washer assembly 82. Pivot gear 90 is prevented from rotating with respect to attachment member 16 by bolt and washer assemblies 82 a, 82 b. A central axis of the pivot gear 90 is coaxial with the first attachment member pivot axis 44. A pawl assembly 92 is pivotally mounted on the inner one of each pair 74 of mating polymeric moldings adjacent pivot gear 90. The pawl assembly 92 comprises a pivot portion 94 having an arcuate first end mounted in a concave recess in a boss 96 on that molding 74 for pivotal movement about a pivot portion axis 96 a parallel with the first attachment member pivot axis 44, and a second end having an arcuate surface 98 that is cylindrically concave about an axis parallel to the first attachment member pivot axis 44 and faces the teeth on the gear 90. The pawl assembly 92 also includes a rocking portion 100 having a cylindrically convex surface 102 on a first side adapted to nest in the arcuate surface 98 of the pivot portion 94 and a plurality of teeth 104 projecting along a second side adapted to engage the teeth of the gear 90. The pivot and rocking portions 94 and 100 are oriented with the axis of the arcuate surface 98 below a straight line between the first attachment member pivot axis 44 and the pivot portion axis 96 a defined by the boss 96, toward which straight line the pivot and rocking portions 94 and 100 are biased by a spring 106 between the molding 74 and the pivot portion 94. This causes the pivot portion 94 to press the concave surface 98 against the convex surface 102 of the rocking portion 100 and the teeth 104 on the rocking portion 100 into engagement with the teeth on the gear 90 to prevent revolving movement of the upper support arm 48 and platform assembly 18 toward a lowered position relative to the attachment member 16. Upward revolving movement of the upper support arm 48 and platform assembly 18 relative to the attachment member 16, however, will pivot the pivot portion 94 against the bias of the spring 106 and move the arcuate surface 98 away from the gear 90 to afford separation of the teeth 104 on the rocking portion 100 from the gear 90 to afford revolving movement of the upper support arm 48 and platform assembly 18 toward a raised position relative to the attachment member 16. Upon reaching that raised position, the spring 106 will again cause the pivot portion 94 to press the concave surface 98 against the convex surface 102 of the rocking portion 100 and the teeth 104 on the rocking portion 100 into engagement with the teeth on the gear 90 to prevent revolving movement of the upper support arm 48 and platform assembly 18 toward a lowered position relative to the attachment member 16.

Rocking portion 100 has a guide surface defining a through slot 110 generally at the axis of the cylindrically convex surface 102, and a side surface defining a recess 112 along the side of the rocking portion 100 opposite the straight line between the first attachment member pivot axis 44 and the pivot portion axis 96 a. The pivot portion 94 includes a pin 114 that projects through the slot 110 and is adapted to engage the guide surface to carry the rocking portion 100 on the pivot portion 94. Pin 114 further provides a pivot axis for the rocking portion 100, such that when upward movement of the upper support arm 48 relative to the attachment member 16 is initiated, teeth 104 positioned opposite the recess 112 initially remain engaged with teeth on the gear 90, while the teeth 104 that are adjacent the recess 112 pivot out of engagement with the gear 90 around the still engaged teeth 104 opposite the recess 112. The molding 74 has a lug or pin 116 adapted to be engaged by the surface defining the recess 112 when the teeth 104 adjacent the recess 112 pivot out of engagement with the gear 90, and thereby restricting further pivoting of the teeth 104 adjacent the recess 112 away from the gear 90 and causing opposite pivot motion of the rocking portion 100 about the pins 114 and 116 to cause the teeth 104 opposite the recess 112 to separate from the gear 90 during further upward movement of the upper support arm 48 relative to the attachment member 16.

Alternatively, the ratchet means 80 can be moved to the disengaged position by manually pivoting the entirety of pawl assembly 92 to move the pawl assembly 92 out of engagement with gear 90. In particular, a cable 120 in a casing or cable housing 120 a (e.g., casings of molybdenum disulfite filled nylon material) is coupled to the pivot portion 94 of the pawl assembly 92. Movement of the cable 120 in the direction of arrow 122 causes the pivot portion 94 to pivot about its axis 96 a to move the arcuate surface 98 away from the gear 90 and cause engagement of the pins 114 and 116 with the surfaces defining the slot 110 and the recess 112, thereby retracting the teeth 104 on the rocking portion 100 to a position spaced from the teeth on the gear 90 (FIG. 6). In one embodiment, approximately 0.050 inches of cable travel in direction of arrow 122 is required to disengage the pawl assembly 92 from gear 90. Actuation of cable 120 is described in greater detail below.

In other embodiments, a slip clutch means is disposed between the gear 90 and the attachment member 16 for affording movement of the upper support arms 48 a, 48 b and platform assembly 18 toward a lowered position relative to the attachment member 16 in response to application of a downward force on the platform assembly 18 above a predetermined minimum force. A suitable slip clutch means is described in U.S. Pat. No. 5,823,487, incorporated by reference herein.

Referring to FIGS. 3, 4, 7A and 7B, lower support arm 50 is secured to platform assembly 18, with tilt adjustment means 130 positioned between the platform assembly 18 and the lower support arm 50. The tilt adjustment means 130 are moveable between a retaining position for limiting pivotal movement of the platform assembly 18 about the first platform pivot axis 40 (defined by the central portion 64 of support member 62), and a release position affording relatively free pivotal movement of the platform assembly 18 about the first platform pivot axis 40.

Referring to FIGS. 7A and 7B, in one embodiment, lower support arm 50 is secured to platform mounting plate 54 by lower support arm mounting brackets 132, which are secured to the platform mounting plate 54 by any suitable means including bolts, screws and the like. Lower support arm mounting brackets 132 each include a curved slot 134 for adjusting the position of attachment of lower support arm 50, and thereby adjusting the tilt angle of platform assembly 18. In one embodiment, curved slots 134 are configured to provide in the range of ±15 degrees of tilt adjustment of platform assembly 18. Lower support arm mounting brackets 132 are illustrated as separate components from upper support arm mounting bracket 60, but may alternately be formed as a single unit with upper support arm mounting bracket 60.

Lower support arm 50 includes a bore 136 at its first end 137, the bore 136 defining the second platform pivot axis 42 when attached to platform assembly 18 via lower support arm mounting brackets 132. For attachment of lower support arm 50 to lower support arm mounting brackets 132, tilt bushings 138 a, 138 b, each having a flange portion 140, a boss portion 142, and an axial through-bore 144 are inserted into bore 136 of lower support arm 50. Boss portions 142 are sized to provide clearance for free rotation of the bushings 138 a, 138 b within the bore 136 of lower support arm 50, and the total length of boss portions 142 exceeds a length of the bore 136. A tilt angle adjustment bolt 150 is inserted through curved slots 134 of the lower support arm mounting brackets 132 and axial through-bores 144 of tilt bushings 138 a, 138 b, and secured by a clamp handle 152. When clamp handle 152 is tightened to compress tilt bushings 138 a, 138 b between lower support arm mounting brackets 132, lower support arm 50 remains free to pivot around tilt bushings 138 a, 138 b, but tilt bushings 138 a, 138 b are secured in position relative to curved slots 134 in lower support arm mounting brackets 132. In this manner, the tilt angle of the platform assembly 18 may be adjusted by moving the clamp handle 152 to a release position, rotating the platform assembly 18 about first platform pivot axis 40 to a desired tilt angle, and then moving the clamp handle 152 to a retaining position to secure platform assembly 18 at the desired tilt angle.

A second end 154 of lower support arm 50 is adapted for connection to attachment member 16 for pivotal movement about second attachment member pivot axis 46. Second attachment member pivot axis 46 is defined by support shaft 160. In one embodiment, a torsion spring 163 (FIGS. 1 and 3) is positioned over support shaft 160, and is configured to upwardly bias the lower support arm 50 and thereby assist a user in lifting the platform assembly 18. Second end 154 of lower support arm 50 includes an elongated slot 162 having a width approximately equal to the diameter of support shaft 160 and a length slightly greater than the diameter of support shaft 160. In one embodiment, support shaft 160 has a diameter of approximately 0.50 inches, and the length of elongated slot 162 is approximately 0.60 inches to allow for approximately 0.10 inches of longitudinal movement of lower support arm 50 relative to the second attachment member pivot axis 46 defined by support shaft 160. In other embodiments, the length of elongated slot 162 may provide for more than approximately 0.10 inches of longitudinal movement of lower support arm 50 relative to the second attachment member pivot axis 46. In still other embodiments, the length of elongated slot 162 may provide for less than approximately 0.10 inches of longitudinal movement of lower support arm 50 relative to the second attachment member pivot axis 46. As described below, longitudinal movement of lower support arm 50 relative to the second attachment member pivot axis 46 is used to actuate cable 120 and move pawl assembly 92 out of engagement with gear 90 (FIGS. 5 and 6).

Referring now to FIGS. 7A-B, 8 and 9A-B, routing and operation of the cable 120 and cable housing 120 a is described. Cable 120 is longer than cable housing 120 a, such that ends of cable 120 extend beyond ends of cable housing 120 a. As described above with respect to FIGS. 5 and 6, a first end 170 of cable 120 is attached to pawl assembly 92. The adjacent end of cable housing 120 a is immovably secured to the upper support arm 48 by any suitable means, such as the illustrated screw and washer assembly 172. A second end 174 of cable 120 is attached to a cable anchor 176 by any suitable means, such as the illustrated screw 178. A spring 180 is connected between screw 178 and second cable end 174 to provide over-travel protection, thereby reducing stress on cable 120 caused by the limited range of movement of pawl assembly 92 (e.g., in the range of 0.050 inches). The end of cable housing 120 a adjacent second cable end 174 is immovably secured to the lower support arm 50 by any suitable means, such as by the illustrated cable clamp 182. The effective length of cable 120 is adjusted by pulling back on cable housing 120 a (relative to second end 174 of cable 120) to remove any slack in cable 120 between cable clamp 182 and screw 178 before tightening cable clamp 182.

Cable anchor 176 is positioned over support shaft 160, and is dimensioned to freely rotate over support shaft 160. In addition, cable anchor 176 is dimensioned to slidably fit between flanges 184 of lower support arm 50, such that lower support arm 50 can slide over support shaft 160 in the longitudinal direction of the elongated slot 162, while the cable anchor 176 remains fixed relative to support shaft 160. Spring 186 (seen in the exploded view of FIG. 7A) is attached to cable anchor 176 and lower support arm 50 by any suitable means, such as screws 188, 190, such that spring 186 biases first end 162 a of elongated slot 162 in lower support arm 50 against support shaft 160 when a user is not raising platform assembly 18 in the manner described below. Spacers 190 fit over support shaft 160 to retain cable anchors 176 inside flanges 184 of lower support arm 50.

Referring to FIGS. 9A and 9B, the platform assembly 18 is shown in the “use” position (FIG. 9A) and the “adjustment” position (FIG. 9B). The upper support arms 48 a, 48 b, provide vertical stability to platform assembly 18 (via releasable retaining means or ratchet means 80), while the lower support arm 50 limits the rotation of platform assembly 18 about first platform pivot axis 40. The weight of the platform assembly 18 and the spring 186 on the lower support arm 50 biases the slot end (162 a) against the support shaft 160. As the platform assembly 18 is raised or lowered, the tilt angle of surface 20 remains constant because of the parallelogram linkage 30 formed by upper support arms 48 a, 48 b and lower support arm 50. That is, the distance between first and second platform pivot axes 40, 42 is equal to distance between first and second attachment member pivot axes 44, 46, and the distance between first platform pivot axis 40 and first attachment member pivot axis 44 is equal to the distance between second platform pivot axis 42 and second attachment member pivot axis 46.

When tilt adjustment means 130 is in the retaining position and platform assembly 18 is rotated by the user about first platform pivot axis 40 approximately 5.50 degrees (FIG. 9B), the lower support arm 50 (which is pivotally connected to second platform pivot axis 42) will move approximately 0.100 inch in the direction of arrow 192 before it reaches slot end 162 b, thereby lengthening the distance between second platform pivot axis 42 and second attachment member pivot axis 46. The lengthening of the distance between second platform pivot axis 42 and second attachment member pivot axis 46 simultaneously increases the effective length of the path of cable 120 because the end of cable housing 120 a closest to support shaft 160 is fixed to lower support arm 50 and is thus also moved further from support shaft 160. The lengthening of the path of cable 120 pulls cable spring 180 a corresponding 0.100 inch. Further upward movement of platform assembly 18 will cause cable 120 to pull on pawl assembly 92 to relieve pressure between pawl assembly 92 and gear 90 and rotate the pawl assembly 92 out of engagement with gear 90, thereby allowing the platform assembly 18 to be lowered or raised to a desired height. When the platform assembly 18 is released by the user, the force of gravity and the force of spring 186 causes platform assembly 18 to rotate back to the use position (FIG. 9A), thereby shortening the path length of cable 120 and allowing pawl assembly 92 to move to an engaged position with gear 90.

The amount of rotation of platform assembly 18 is dependent upon the necessary change in the effective path length of cable 120 required to disengage the pawl assembly 92 from gear 90. The necessary change in the effective path length of cable 120 is dependent upon the particular geometry of the pawl assembly 92 and gear 90, and the distance pawl assembly 92 must be moved to cause disengagement. The length of elongated slot 162 controls the effective path length of cable 120 and, as noted above, the length of elongated slot 162 may be greater or less than the exemplary 0.10 inches that results in approximately 5.50 degrees of rotation of platform assembly 18 in the exemplary embodiment. Thus, in other embodiments, the amount of rotation of platform assembly 18 about first platform pivot axis 40 required to release pawl assembly 92 from gear 90 may be greater than about 5.50 degrees or less than about 5.50 degrees. In one embodiment, the rotation of platform assembly 18 is in the range of 2 to 8 degrees of rotation about first platform pivot axis 40.

Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof. 

1. An articulated support assembly adapted for adjustably supporting a computer keyboard from a horizontal support surface, the support assembly comprising: an attachment member adapted to be attached to the horizontal support surface; a platform assembly having an upper surface adapted to have a computer keyboard supported thereon, the upper surface having a predetermined orientation with respect to the horizontal support surface; a vertically swingable parallelogram linkage having elongated first and second links each having a first end and a second end, the first ends of the elongated first and second links pivotally interconnected to the platform assembly, and the second ends of the elongated first and second links pivotally interconnected to the attachment member, such that the first and second ends of the first and second links each have a pivot axis, and such that the linkage allows vertical displacement of the platform assembly relative to the support surface while maintaining the predetermined orientation of the upper surface; a releasable retaining means coupling the first link to the attachment member, the releasable retaining means moveable between an engaged position for preventing vertical movement of the platform assembly toward a lowered position relative to the horizontal support surface, and a disengaged position for allowing vertical movement of the platform assembly toward either a lowered or a raised position relative to the horizontal support surface; and means for altering the distance between the pivot axes of the second link, wherein altering the distance between the pivot axes of the second link moves the releasable retaining means between the engaged position and the disengaged position.
 2. The articulated support assembly of claim 1, wherein the means for altering the distance between the pivot axes of the second link comprises an elongated through-slot at one of the first and second ends of the second link, the elongated slot configured to receive a shaft defining one of the pivot axes of the second link, the shaft movable between a first end of the slot having defining a first inter-axis distance and a second end of the slot defining a second inter-axis distance.
 3. The articulated support assembly of claim 2, wherein the shaft is movable between the first end of the slot and the second end of the slot by pivotal movement of the platform assembly about the pivot axis at the first end of the first link.
 4. The articulated support assembly of claim 1, wherein the releasable retaining means comprises: a height adjustment gear having radially outwardly projecting gear teeth, the gear attached to the attachment member and coaxial with the pivot axis of the second end of the first link; a pawl assembly attached to the first link and configured to engage the gear teeth; a biasing member urging the pawl assembly toward the gear teeth; and a cable attached to the pawl assembly and configured to pull the pawl assembly away from the gear teeth, the cable extending from the pawl assembly along a cable path to the second link, the cable path alterable between a normal cable path allowing engagement of the pawl assembly with the gear teeth, and a lengthened cable path causing the cable to pull the pawl assembly away from the gear teeth; wherein altering the distance between the pivot axes of the second link alters the length of the cable path between the normal cable path and the lengthened cable path.
 5. An articulated support assembly adapted for adjustably supporting a computer keyboard from a horizontal support surface, the support assembly comprising: an attachment member adapted to be attached to the horizontal support surface; a platform assembly having an upper surface adapted to have a computer keyboard supported thereon; a first support arm adapted for mounting the platform assembly on the attachment member, a first end of the first support arm pivotally mounted to the platform assembly for pivotal movement of the platform assembly about a first platform pivot axis, a second end of the first support arm pivotally mounted to the attachment member for pivotal movement about a first attachment member pivot axis; a second support arm adapted for mounting the platform assembly on the attachment member, a first end of the second support arm pivotally mounted to the platform assembly for pivotal movement of the platform assembly about a second platform pivot axis, a second end of the second support arm pivotally mounted to the attachment member for pivotal movement about a second attachment member pivot axis; wherein the first platform pivot axis, second platform pivot axis, first attachment member pivot axis and second attachment member pivot axis are parallel to each other, and wherein the first and second platform pivot axes, the first and second attachment member pivot axes, and the first and second support arms are positioned to define a parallelogram linkage; and first releasable retaining means between the first support arm and the attachment member, the first releasable retaining means moveable between an engaged position for preventing rotating movement of the first support arm toward a lowered position relative to the attachment member, and a disengaged position for affording rotating movement of the first support arm toward either a lowered or a raised position relative to the attachment member; wherein the first releasable retaining means is moved from the engaged position to the disengaged position by pivotal movement of the platform assembly about the first platform pivot axis.
 6. The articulated support assembly of claim 5, wherein the first releasable retaining means comprises: a height adjustment gear having an axis and radially outwardly projecting gear teeth, the gear attached to the attachment member and coaxial with the first attachment member pivot axis; and a pawl assembly attached to the first support arm and configured to engage the gear teeth; wherein the first releasable retaining means is moved to the engaged position by moving the pawl assembly toward the gear and causing engagement of the pawl assembly with the gear teeth, and wherein the wherein the first releasable retaining means is moved to the disengaged position by moving the pawl assembly away from the gear and causing disengagement of the pawl assembly from the gear teeth.
 7. The articulated support assembly of claim 6, further comprising: a biasing member urging the pawl assembly toward the gear; and a cable attached to the pawl assembly and configured to pull the pawl assembly away from the gear, the cable extending from the pawl assembly along a cable path to a cable anchor in fixed relationship to the attachment member, the cable path alterable between a normal cable path allowing engagement of the pawl assembly with the gear, and a lengthened cable path causing the cable to pull the pawl assembly away from the gear; wherein pivotal movement of the platform assembly about the first platform pivot axis alters the length of the cable path between the normal cable path and the lengthened cable path.
 8. The articulated support assembly of claim 7, wherein pivotal movement of the platform assembly about the first platform pivot axis alters the distance between the second platform pivot axis and the second attachment member pivot axis.
 9. The articulated support assembly of claim 7, wherein the cable path is altered between the normal cable path and the lengthened cable path by pivotal movement of the platform assembly about the first platform pivot axis in the range of 2 to 8 degrees of rotation.
 10. The articulated support assembly of claim 5, further comprising: a third support arm adapted for mounting the platform assembly on the attachment member, a first end of the third support arm pivotally mounted to the platform assembly for pivotal movement of the platform assembly about the first platform pivot axis, a second end of the third support arm pivotally mounted to the attachment member for pivotal movement about the first attachment member pivot axis; and second releasable retaining means between the third support arm and the attachment member, the second releasable retaining means moveable between an engaged position for preventing rotating movement of the third support arm toward a lowered position relative to the attachment member, and a disengaged position for affording rotating movement of the first support arm toward either a lowered or a raised position relative to the attachment member; wherein the second releasable retaining means is moved from the engaged position to the disengaged position by pivotal movement of the platform assembly about the first platform pivot axis.
 11. The articulated support assembly of claim 10, wherein the second support arm is positioned between the first and third support arms.
 12. The articulated support assembly of claim 5, further comprising tilt adjustment means joining the second support arm to the platform assembly, the tilt adjustment means movable between a retaining position for limiting pivotal movement of the platform assembly about the first platform pivot axis and positioning the upper surface of the platform assembly at a predetermined orientation relative to the attachment member, and a release position affording relatively free pivotal movement of the platform assembly about the first platform pivot axis.
 13. The articulated support assembly of claim 12, wherein when the tilt adjustment means is in the retaining position, the limited pivotal movement of the platform assembly about the first platform pivot axis is sufficient to move the first releasable retaining means from the engaged position to the disengaged position.
 14. The articulated support assembly of claim 13, wherein pivotal movement of the platform assembly about the first platform pivot axis alters the distance between the second platform pivot axis and the second attachment member pivot axis when the tilt adjustment means is in the retaining position.
 15. The articulated support assembly of claim 13, wherein when the tilt adjustment means is in the retaining position, the pivotal movement of the platform assembly about the first platform pivot axis is in the range of 2 to 8 degrees of rotation.
 16. The articulated support assembly according to claim 5, wherein said first releasable retaining means comprises: a height adjustment gear having an axis and radially outwardly projecting gear teeth, the gear attached to the attachment member and coaxial with the first attachment member pivot axis; and a pawl assembly including a pivot portion and a rocking portion, the pivot portion having a first end mounted on the first support arm for pivotal movement about a pivot portion axis parallel with the first attachment member pivot axis, and a second end having an arcuate surface that is cylindrically concave about an axis parallel to the first attachment member pivot axis and faces the teeth on the gear, the rocking portion having first and second sides, a cylindrically convex surface on the first side adapted to nest in the cylindrically concave surface of the pivot portion and a plurality of teeth projecting along said second side adapted to engage between the teeth of the gear; wherein the pivot portion and the rocking portion of the pawl assembly are oriented with the axis of the pivot portion arcuate surface below a straight line between the first attachment member pivot axis and the pivot portion axis to cause the concave surface of the pivot portion to press against the convex surface of the rocking portion and thereby engage the teeth on the rocking portion with the teeth on the gear to prevent revolving movement of the first support arm toward a lowered position relative to the attachment member, while upward movement of the first support arm relative to the attachment member causes the pivot portion to pivot and move the arcuate surface away from the gear to afford separation of the teeth on the rocking portion from the gear and afford revolving movement of the first support arm toward a raised position relative to the attachment member.
 17. The articulated support assembly according to claim 16, wherein the rocking portion has a guide surface defining a through-slot generally at the axis of the cylindrically convex surface and a side surface defining a recess along the side of the rocking portion opposite the straight line between the first attachment member pivot axis and the pivot portion axis, wherein the pivot portion includes a pin projecting through the rocking portion slot and adapted to engage the guide surface to carry the rocking portion on the pivot portion and provide a pivot axis for the rocking portion to pivot the teeth adjacent the rocking portion recess out of engagement with the teeth on the gear.
 18. The articulated support assembly according to claim 17, wherein teeth on the rocking portion opposite the recess engaged with teeth on the gear when upward movement of the first support arm relative to the attachment member is initiated, and the first support arm has a pin adapted to be engaged by the surface defining the rocking portion recess when the teeth adjacent the recess pivot out of engagement with the gear to restrict further pivoting of the teeth adjacent the recess away from the gear and cause opposite pivot motion of the rocking portion about the pins to cause the teeth opposite the recess to separate from the gear during further upward movement of the first support arm relative to the attachment member.
 19. The articulated support assembly according to claim 16, wherein the first releasable retaining means is moved to the disengaged position by pivoting the pivot portion to move the arcuate surface away from the gear and cause retraction of the teeth on the rocking portion to a position spaced from the teeth on the gear. 